Refrigerator container cooled by carbon dioxide ice



C. B. HALL May 23, 1950 REFRIGERATOR CONTAINER COOLED BY CARBON DIOXIDEICE Filed Aug. 8, 1947 6 Sheets-Sheet 1 FIG.|

lNVENTOR 3 'CHARLES B.HALL

wfi" A%NEY c. B. HALL I May 23, 1950 REFRIGERATOR CONTAINER COOLED BYCARBON DIOXIDE ICE 6 Sheets-Sheet 2 Filed Aug. 8', 1947- FIG. 6

INVENTOR CHARLES E. .HALL RNEY y 23, 1950 c. B. HALL 2,508,385

REFRIGERATOR CONTAINER COOLED BY CARBON nxox'm: I-CE Fill ed Aug. 8,1947 e Sheet-Sheet s INVENTOR CHARLES B. HALL I May 23, 1950 c. B. HALLREFRIGERATOR CONTAINER COOLED BY CARBON DIOXIDE ICE Filed Aug. 8, 1947 GSheets-Sheet 4 INVENTOR CHARLES B. HALL BYJZQ/ fig ATTORNEY y 1950 c. B.HALL 2,508,385

} REFRIGERATOR CONTAINER COOLED BY CARBON DIOXIDE ICE Filed Aug. 8, 19476 Sheets-Sheet 5 INVENTOR CHARLES B. HALL 'c. B. HALL May 23, 1950REFRIGERATOR CONTAINER COOLED BY CARBON DIOXIDE ICE s Sheets-Sheet 6Filed Aug; ,8, 1947 IA GRADlENT- OUTER INSULATION INNER CASING SHELLFIG. l4

GRADIENT-STEPI IFARAIDIENT-STEPZ 75 POUNDS (a) H INNER INSULATION SHELLAPPROX. 3/4 OF CO1 F IG.

OUTER CASING V2 THE INSULATION REFRIGERANT 1/ OF co, CONTAINER QLGRADli-lIgT- STEP 2 GRADIENT-STEP 3 GRADIENT-STEP l CONDUCTOR PLATE DUCTVa CASING INSULATION v g r g c'roa v, INNER SHELL INSULATION GROOVE) g sgl OUTER CHAMBER CHAMBER FIG.-|6

INVENTOR CHARLES B.HAI L %!7 5?? ORNEY Patented May 23, 1950REFRIGERATOR CONTAINER COOLED BY CARBON DIOXIDE ICE Charles B. Hall,Chicago, 111.

Application August 8, 1947, Serial No. 767,397

11 Claims.

This invention relates generally to refrigerator containers, and moreparticularly to storage and shipping containers for use in thetransportation of quick frozen foods, and all other products, requiringconstant freezing, zero or sub-zero temperatures but usually from F. tominus 20 F. The invention further relates to improvements in methods andapparatus for use with solid refri erants, such as carbon dioxide (solidCO2 or Dry Ice), and the like.

A principal object of this invention is to provide a method ofrefrigerating by means of solid refrigerants that shall be moreefiicient than prior methods and shall materially extend the period oftime for which a given quantity of the refrigerant will maintain thedesired low temperature in the lading space of the refrigeratorcontainer.

The invention described and claimed herein resides in a novel way ofapplying all of the refrigerating properties of solid carbon dioxide(Dry Ice) and of the carbon dioxide gas sublimated from the solid carbondioxide, by interposing the refrigerants in such manner as to interceptheat passing into the interior of the container from the outsideatmosphere, causing such heat to be returned to the outside atmosphereinstead of continuing into the interior of the refrigerator container,and the apparatus designed to interpose the refrigerants and toaccomplish the heat transfer to the carbon dioxide gas being vented toan outside gas system or the outside atmosphere.

The invention described and claimed herein further resides in thedisclosure of an application of the gradient step-down principle ofrefrigeration, wherein the normal gradient of a refrigerator containeris sub-divided into two or more gradient steps.

Another principal object of this invention is the reduction of thegradient inducing heat transfer to the prime refrigerant of arefrigerator container through the application of the gradient step-downprinciple. It is an established fact in refrigeration that the greaterthe gradient, the differential in temperature between the outer surfaceof the container and that of the interior of the container, the morerapid the rate of heat transfer to the refrigerant. It is a purpose ofthis invention to divide the gradient of the container into steps, byinterposing secondary chambers being chilled by gas Sublimated from thesolid carbon dioxide,to cause the formation of two or more gradientsteps, only one of which will induce the transfer of heat to the primerefrigerant.

Another object of this invention is the establishment of a closed gassystem, including suitable chambers, interposed to intercept heat, thesame gas being reapplied to the same path of heat in successive steps,in such manner that the gradient of the refrigerator container will besub-divided into a series of steps.

Another object of this invention is to furnish a means for bringing thegas sublimated from solid carbon dioxide under control, housed insuitable refrigerating chambers, to act as a secondary refrigerant.

Another object of this invention is to provide a refrigerator containerfor the transportation of quick frozen foods and other productsrequiring a constant freezing, zero or sub-zero temper-' ature, andusing a solid refrigerant, which retains the carbon dioxide gas in aclosed circuit to preclude the contact of said gas with the foodproducts in the lading chamber, a condition which causes a drying-outand desiccation of the products.

A further object of this invention is to furnish a means for the controlof the temperature of a refrigerator container by the use of a pressurecontrol valve in a closed gas system, designed to release Sublimated gasfrom the prime refriger-' ant chambers intermittently to the secondaryrefrigerating chambers, the variable frequency of this intermittentrelease being an effective temperature control.

A further object of this invention is to provide a sealed refrigeratorcontainer for the transportation of quick frozen foods and otherproducts requiring constant freezing, zero or sub-zero temperatures,that will assure the maintenance of absolute sanitary conditionsthroughout an intransit period.

A further object of this inventionis to provide a refrigerator containerfor quick frozen foods and other products requiring constant freezing,zero or sub-zero temperatures, which will give adequate air circulationaround the refrigerated products to insure absolute minimum growth ofmolds, inherent in cold storage operations.

A further object of this invention is to provide a refrigeratorcontainer, a multiple number of which may be used for the transportationof carload-lots of quick frozen foods and other products requiringconstant freezing, zero or sub-zero temperatures, and one or more ofwhich may be used for less-than-carload-lot shipments.

Another object of this invention is to provide a means for the evendistribution of the refrigerant of a carload-lot shipment of quickfrozen foods shipment remaining after partial unloading, and withoutappreciable loss of refrigerant due to ar:

tial unloading.

A still further object of this invention is to, proa vide an outside gassystem to surround top perimeter of a multiple number"o'frefrigeratorcontainers placed in a standard freight caiyto be,

suspended from the containers, between the cont ainers and the sides andends of the freight car, to. be charged-withearboh dioxide gas ventedfrom the gas system of refrigerator containers operated on thewgradientstep-down principle, fer the purpose of. providing supplementalrefrigerationand insulationfor the refrigerator containers placed in thefreight car.

And still another obj'ecto thisiinvention is to provide a means forinstalling a supplemental protective layer of blown insulation arcund,above and beneath: a multiple number of refrigerator containers placedin a standard freight car; the

minute openings between the particles of iinsiula tion to' befilledwithcarbon digxide' gas, released from an'outs'fide gas system'suspendedaround the top perimeter of the refrigerator containers.

Prior inventions have jmade a partial use of gaseous carbon 'dioxidatosupplement the refrigerant action of the "solid -carbc jn dioxide, by

releasing the sublimated gas intoJthe lading' chamber, by releasing thegas into a secondary refrigerant such as a brine, by passing the gasaround an area provided-between the insulating walls and the ladingchamber, by releasing the gas into the insulate a ea, and in many otherdevices, but in no prior method is found the full utilization of the,gas as provided in this gra dientstep-dovvl'i principle. l

Still other and more specific objects and advantages of. this inventionwill become apparent from" the description hereinafter set forth of oneembediment or example thereof, and from the accompanying drawingstowhich the descriptidn has ref l fi f V In the drawings;

Fig, 1 is an exterior fr nt andside angle view with'the door closed, ofone embodiment of a refrigerator container;

Fig. 2 is a front View of the same container, with the door open;

Fig. 3 represents 9, vertical sectional view from the front taken online3-3 of Fig. 4;

Fig. 4 representsa vertical sectional View from the side taken on line4.,4'of Fig. 3;

Fig. 5 represents 'a fragmentary perspective,

view of the Solid carbon dioxide" chambers and the piping system for therelease or the sub-v limated' gasto the secondaryrefrigerant chambers;

Fig. 6 represents an enlarged, fragmentary cross section of a side wall,showingthe assembly of the secondary refrigerating'chambers;

Fig. 7represents'a'perspective'view of the component parts of the firstsecondary refrigerating chamber, or groovedchjambemf "periods, andduring temporary delay .in loading for long-distant, carload-lotshipments. Be-

Fig. 8 represents a perspective view of the com ponent parts of thesecond secondary refrigerating chamber, or duct chamber;

Fig. 9 represents a perspective, fragmentary view of the over-all gassystem;

Fig. 10 represents a vertical cross sectional view of a freight carloaded with refrigerator containers, taken from the side of the car;

Figllrepresents a vertical crosssectional view of afreight car'loadedwith refrigerator containers, taken from the end of the car;

i Fig. 12 represents a fragmentary, perspective view of an outside gassystem, charged with carbo'n dioxide gas through a flexible connectionjoined" to'the vent of the refrigerator container;

'Fig." 13' represents a fragmentary, transverse view of a loaded freightcar, with the outside gas system"and supplemental blown insulation inplaeef, taken from the end of the car on a setback basis;

Fig. 14 is a diagrammatic illustration of the path and transfer of heattothe refrigerant in an ordinary refrigerator container;

Fig. 15 is a diagrammatic illustration of the path and transfer of heat,as it would'occur, if

it were practical to install a part of the refrigerant between divisions"of the insulation in the walls of a refrigerator container'j'and.

Fig. 16 is a diagrammatic illu'stration of the path and'transfer of heatto the secondary refrigerants and to the primerefrigirant', marefri'gerator container embodying'the apparatus for the functioning'of thegradient 'stepedcw'n principle V The quick frozen food industry.hasbecome one of the fastest growing industriesina' little more thanone decade, and givesprornise of continuingfeven accelerating, thisrapidp'ace of growth. One of the major problems of the industry is themaintenance orconstant, relatively low temperaturefrom the moment ofquick freezing until the'time of intentional ,dewfrost'ing for eatingpurposes. This problem isrea'son'ably simple in the processors plant; inthe wholesalers "storage and in the retailers display To date, themaintenance of these constant low temperatures during iiietransitperio'd'shas 'beenexceedingly difficult, and "much of the inferiorduality product which has appeared on the: market hashad this inferiorquality impartedfto it. 'duringperiods. of transportation.

Thisinvention will furnish the necessary refrigerated protectiontoallquick frozen foods and other products. v requiring constant freezing,zero and sub-zero temperatures, during ill-transit and unloading atshipperand consi nee terminal points' Shipments of quick frozenfoodsandthe likev may be readily classifiedinto carloaddot ship merits,and less-thanwarload-lot "shipments.

Carload-lots are usually shipped y freight; less than-carload-lots areusually lshipped by. express, truck or 'air. Theperiod of'in-transititime'for less-than-carload-lots is usually brieferthan thatcause, of these two general classifications, the description whichfollows hereinafter is'idivided into two sections, first, the operationswhich are common to all s n s, andseeongl, the, additional p t ction prvided for can d lete.

By making use of therefrigeratorcontainer of this jinventiom'allshipmentsof quick frozen foods, and other products, re u ring constantfreezin Zero or subs-Zero, tern eriattires may; be

made in ordinary freight cars, express cars, ordinary'trucks and freightplanes; refrigerated cars and; refrigerated trucks will not be required.

Therefrigerator containers designed and used TOI'jCfiI'lOEid-IOtshipments must of necessity be of a size which will permit the use ofthe maximum space of the freight car, and with this considerationin'mind, it has been found that a container of a'size'which will permitthe placement of eight such containers from end to end in the car, andtwofrom side to side, utilizes the space in the average freight car toexcellent advantage, although it' is obvious that a container for thispurpose need not be confinedto these dimensions. Containers of this sizemay be readily handled by either manual or automatic lift trucks, andsince such shipments will usually originate and terminate at coldstorage terminals equipped forhandling suchshipments, no difficulty willbe encountered.-

The refrigerator containers designed and used for less-than-carload-lotshipments, will usually be of a size more conveniently handled in LCLtraflic, thoughthe larger container may be used where practical. Theprinciples of construction and of operation are identical, except forthe added exterior insulation and refrigeration provisions made in thefreight car for thehandling of long-distant carload-lot shipments.

The refrigerator containers are extremely durable in construction towithstand the severe handling involved in transportation and yet theover-all weight of the container is low due to the relativelylightweight material used in construction.- It is important thatexcessive tare not be added to the weight of the shipment.

In the form chosen for disclosure herein, the invention is embodied in arefrigerator container C having an outer casing I of light weight butdurable metal or like material, reinforced with bracing members as isthe practice in such construction. The container C has an inner shell 22that is of lighter weight metal or other material and is also bracedwith supporting members 23, anda door 3 afforded that is constructed toclose flush with the outer casing, being secured by locked nuts fittedover threaded studs 5 protruding from the Walls and inserted throughrecessed openings in the door. The outer casing or shell I', and theinner shell 22 are supported in conventional heat-breaker relation, andthe same is true with respect to the inner and outer walls of the door3. Provision is made in the form of a rubber gasket 6 for sealing thedoor tightly, toninsure air-tight protection to the lading compartmentduring transit periods, and recessed gripping wells 1 are provided forhandling door... Each container is mounted on skid legs-4 formed by theextension of the corner bracing members, to permit handling with me--.chanical equipment. An outer gas vent 8 is recessed in the side or topof the outer casing for protection, andis threaded to permit theattachment of flexible pipe connections 55 in the freight car as willhereinafter be described in detail. An emergency pressure release vent 9also afforded and is also recessed in the side or top of the outercasing.

Since no object on the exterior of the containers C protrudes beyond thesurface of the outer casing, when loaded into freight cars, it ispossible to, place them flush against one another, forming a compactunit set away from :the ends 49 and sides 50 of the car, with a six oreight inchspace on .all sides of the container,

6 and with the doors of the containers turned inwardly against anothercontainer. This arrangement materially reduces the area of the containersurfaces in the freight car exposed to heat transfer.

In the carload-lot containers, one or more solid carbon dioxide chambers(prime refrigerant chambers) H are provided, however, in the smallerless-than-carload-lot containers, only one prime refrigerant chamber isnecessary. The prime refrigerant chambers II are suspended in brackets12 from the top of the inner shell 22 and because of the relativelyheavy weight of these loaded chambers, and due to the shunting andjarringof the freight cars in transit, and therefore of the refrigeratorcontainers, substantial bracing members l3 are placed from the chambersto the inner shell and between the two chambers.

The doors [4 of the prime refrigerant chambers are arranged with rubbergaskets I6 and mechanical sealing devices I5, to insure gastight sealingof the doors of the prime refrigerant chambers. Suitable piping I1 isprovided to exhaust the Sublimated gas from the prime refrigerantchambers and an emergency pressure release valve 19 is installed in thepiping circuit to cause the venting through the vent 9 to the outsideatmosphere of any undesired pressure of gas which might accumulate.

Under and in accordance with the present invention the gaseousrefrigerant that is sublimated from the solid carbon dioxide Within thechamber or chambers ll serves first, of course, to cool the walls of thechamber or chambers l I, thereby to cool the ambient air Within thelading chamber of the container, and such gas is thereafter passedsuccessively to a plurality of secondary refrigerating chambers that aredisposed in heat transfer relation to a similar plurality of wallslocated in spaced relation to each other in the space between the innerand outer shells of the container C. Thus in the form herein disclosed,each wall of the container C has a pair of plates or walls 34 and 34Adisposed therein in spaced relation to each other and to the inner andouter shells of the container, and these walls are made from a materialsuch as metal so as to be good conductors of heat. The wall 34 isclosest to the inner shell 22 and has a refrigerating chamber 35associated in heat transfer relation thereto; while the wall 34A isdisposed between the wall 34 and the outer casing I and has a secondaryrefrigerating chamber 39 associated therewith in a heat transferrelation. The gaseous refrigerant is under the present invention passedfrom the chamber or chambers I [through the chamber 35, then through thechamber 39, and is then vented from the container C by the vent 8 aswill hereinafter be described in greater detail.

It will be observed that a flexible pipe connection 20 has been madefrom the gas exhaust piping to the secondary refrigerating apparatus orchambers of the refrigerator container door for the input of carbondioxide gas and another flexible connection 2| is provided for ventingthe gas from the secondary refrigerating apparatus of the door.

It has been found that this invention functions well for certaintemperatures and certain purposes without the installation of a pressurecontrol valve IS in the closed gas system, however, the installation ofsuch a valve is preferred, for by regulation of such valve l8, the

me ts:

d; s in t e se e da e r ee e s .e ee bersand y he ch n ed; withc u b" it ney a m v be requi d .te me e eiett eel sired. temperature within therefrigerator container lading compartment. U n a i e e ina m mbe ce e nat d r he 4 e ede ee taet o n s et eiene .elie bracing members "23,andto these S shaped sun Porting mem e a e t tt eh ti ene ei el 1 5??? rs25 o receiving endhe slin thela iee trays '6 s el e of the e taie Fresh;9 shelves; areof open construction to "permitfree circulation of airaround'thela ding E rotrudin g contacts 21 "are attached to the; topsanol bottoms cf the sides of the trays, to;i nsure further aircirculation and togive'firmstorage in the conai or e e h t dur ng t nst:

1 e se pf nnove i e nd y r ri atin chambers 35 and 39, installed in theside walls of therefrigeratorcontainenand to insure a dryness of theinsulation material in the side walls at all times, provisionis made forthe periodic drying of the insulation by forcing a, slow stream ofheated, dry airinto the insulated walls for which purpose anormallyclosed insulationdryer inlet; 28'and a normally closedinsulationdryer outlet-29 areprovided in the inner shell-of therefrigerator'container. h

The side walls a-nd'door of the refrigerator container areconstructed-with three layers ofinsulation Si, 32-, and -3-3,Fig. l6,between which-are interposed the two walls 34' and 34A Wit1lft1lQi1secondary refrigerating chambers 35 and 39. This insulation may take theform of reflective insulatioma's indicated'in Fig.: 6,-or may1 taketheform of fibrous or like material in either bulk form-'or'inshe'ets, asindicated-in Fig. 16. It will be-notecl in'Figs. "6 and lfithat onelayerof insulation 3 iis'placed outside-of theinner} shell 2-2, after whichthe first of thesecondary refrigerating-chambers' 35 and'its heattransfer wall34 are installed against shoulders 46. This chamber 35 isherein more specifically termed 'the -grooved chamber, dueito the natureof its "construction, and is --mcre fully-described hereafter. This isfollowed by another layer of insulation 32 and then theinstallation-ofthe Second secondary refrigerating" chamber B-Wa'ndtitsheat transfer wall 34A, the-chamber 39: being herein designated asthe-duct chamber; and more :fully'described later. Another layer ofinsulation 33" is placed between this "second; secondary refrigerating"chamber 39 and the outer casing -i. The insulations-pref erred in 'thisinvention are those known "astFerro-Therm or Fiberglas, however, it has"been found that those commercial products known-as Dry zero, rock*wool; and several others-will'serve the purpose. -Ferro-Therminsulation -is" commercially available and comprises 'a: -ste'e1*sheetcovered onone-face b'y an -alloy;coatingof "lead and tin with afinishing film of palm oil overthis coating. 'Fibergl'as insulationisalso-commerci'allyavailableand' is afiordedby abody of relatively fineglass-fibers that areusually depositedfin the'form' of a mat or b'attsothat thisbattmay lee-"disposedin the'space between two walls. "Dry Zeroinsulation 'is available commercially: and is afforded in either bulk or-battform. The Dry Zero material is made from fibers of-the pod'of thetropical *Ceiba' t'ree. Rock "wool similarly available in either" bulkor 'batt for'm; F and this material is *in the form of *fib'ers "made Tfrom a mineral or rochrrnaterial. l 4

The piping ll provided for' the' escape oI the carbon dioxide gas *from*the prime refrigeranteeembe U "th n w seeee xeeeeae chamber 35 and theductsecondary refrigerating w es bte e lexl ue e sfa m the-Prime re ue!- e'e 'eheme re 1! releieseexeneee esee u o the dpen'ing of thepressure control valve 18, is res e. int t e a eeve veeee e c rvix. risret umber-e5 and theme chi herteme tur a .eete ee m mbe s? i fe eeq thou h. the ee nee n, Mime the e eee erx r e ti s chambe te hwhieh ceas te P 9 stil -h er tem eratur -Je r eha zb 3,9 o be forcecl out throughtheconnection '45 to be reeeiefeqth e ht e eneer v r c .7 c

While hetwe. eee nciery; efr era n c e t amed-i3; e o im e u 9 s i x ereienv ztber fe e he r i e sn.;are s h siii l 'e t- The first. of th e dry v e ret e' hem e si sneWn-es e i e d a e has a specific reason forits *design. A block of aluminum; or other good heat conductor material,approximately ;inch thick "and l0 -inehes wide! s .e t with: aneherooved patt rn .6; s she j in Figure fl, -'I -his block'is thenwelded er iea l st ei en erofsa; nt grpla ei o a surf aee; area of'the'lengthand width of the inee imensi eeei the si ewa11, -withthegrooved surface placed ;-inwardly toward the conductor mounting plate34,; to form-the equivalent {of a ;inch coi l mounted on "a conductormounting plate. :In-;f act,-= a coil so mountedbut withfa good heatconductor 'joint' throughout 'may be used.

This small-path-for the passageof the gas downward, when ireleased underpressure from the prime-refrigerant ichambers; for the purposeof-forcingfall of'themld; highertemperature gas forward in thegasgsystem;withoutpermitting counter currents of thehigher temperaturegas to;moveupward or backward in 'the system. 7 a The second "of the."secondary. "refrigerating chambers "39* is constructedbvwelding *aduct of aluminum-qflor-othergood heat-"conductingmateriaL-approximatelyin'Ghdeepahd 10'inches j'vvide,1ivertically 'to a"con'cluctor mountingplate 34A "of the same-good*heatnondticting*metaL a plateo'f *t-helength andwidlmbfthe inside'di'm'ensions of 'the sideg walk; When gas'isforcdoutbf the first; secondary "refrigerating- 'chainber 35, at theexit :3 8"through the'poor heat conductor *connectio'n i'd; it ri'ses'from the entry l in" the "duct of the seccnd "secondaryrefrigeratingchamber 39',"the warmer gas' being-of lighter-weight: to bevented nomthe refrigerator? container through the exit 42 and the vent3. Whfle certa'in dilnehsicns are usedin the' foregoing description "forpurnoses of"explanation; is* obvious thse'seoondary 'i'frigeratirig"=chambers "may be *co'nstructed -inwariofis sizes and propbrtions 'asfl't thei'equireni'ents'; :"Anotlier' princifial' feature of thisinventiofils the' novel" method for brawning -aealtibnarinsulation andrefrigeration for a mass of refrigerator containers, in the storage ofsuch containers in the freight car. This method is only possible becauseof the nature of the construction of the refrigerator container of thisinvention and its principles of operation, and for that reason isincluded in this application as another of the principal claims of thiinvention.

The loaded refrigerator containers C are shored into the freight carthrough the use of planking 53 and mechanical Jacks 54, as shown inFigure 13. This is a progressive operation, performed as the containersare moved into the car. The following additional operations are alsoperformed progressively as each container is placed in the freight car.

Perforated piping 56, suflicient to extend around the perimeter of themass of refrigerator containers loaded into the freight car, isprovided. This is jointed in practical lengths, approximately the lengthof one sidewall of the refrigerator container, of a type easily joinedand secured by a friction fitting 51, or some other simple means ofconnection. Each length has a connection 58 for the attachment of aflexible pipe 55, the other end of each flexible pipe being connected tothe vent 8 of one of the refrigerator containers.

A perforated and screened metal cover 59, round except for a flatsurface on the side toward the container, with a screened opening in thebottom, is provided in similar lengths and is similarly capable of beingeasily joined 60, to surround the perforated piping and disposed bymeans of bracing members about two inches from the circumference of theperforated piping. Strap hangers 62 are arranged to suspend theperforated piping 56 and the metal cover 59 from the recessed wells I l!of the outer casing of the refrigerator containers. When all containershave been loaded into the freight car, an outside gas system ofperforated piping with protective metal covering, with screened bottomopening, will surround the perimeter of the mass of refrigeratorcontainers, near the top of said containers, and disposed between theouter casing of the mass of containers and the sides and ends of thefreight car.

As containers are loaded into the freight car and the outside gas systemis installed and connected, a layer of loose insulation is blown intothe freight car in all open area between the mass of containers and theroof, floor, ends and sides of the freight car, the outside gassystembeing comcover 59, and from the screened openings of the" metal coverinto the blown insulation 6! surrounding the mass ofrefrigeratorcontainers, to seep through the minute openings between the particles ofblown insulation to form a blanket of insulation and refrigeration tofurther inter-' cept heat entering through the walls of the freight car,before such heat can come into contact with the surface of therefrigerator containers.

Inthe operation or use of the containers of this invention, though theyare of simple mechanical construction, care should be exercised in theirpacking, charging and loading to secure the best results. It isdesirable to pre-cool the container "in a cold room of approximatelyminus 20 F.

Such heat, if any, will by thelaws of nature, rise g temperature, toinsurea constant freezing, zero or sub-zero temperature immediately uponthe lading being placed in the container. When the refrigeratorcontainer has been brought to the desired temperature, the ladingcompartment should be thoroughly sterilized with an ultraviolet raylamp.

The lading which has been maintained at low temperature is then packedin the container trays and the trays positioned in the ladingcompartment of the refrigerator container. The prime refrigerantchambers are then charged with solid carbon dioxide (Dry Ice) and thesechambers are sealed, after pressure valves have been checked. Carbondioxide gas is then forced through the gas system, under pressure, toremove all air or warm gas from the system and to reduce the temperatureof the gas system to the desired point. The gas system is then connectedto the prime refrigerant chamber gas outlet. The lading compartment dooris closed and sealed, to insure that this compartment will remainair-tight during transit.

If the shipment is less-than-carload-lot, the container or containersare then ready for shipment. If the shipment is a carload-lot, theloading operation requires further description.

For carload-lots, further insulation and refrigeration is provided.Beginning at the ends of the car and loading toward the middle, loadedrefrigerator containers are placed two across in the car. Mechanicaljacks and planking are used to shore in the containers, car dimensionsbeing taken into consideration, to divide equally the surplus spacewhich will remain around the mass of loaded containers, at the ends andsides of the car.

Joints of perforated piping, to form the outside gas system, aresuspended by the strap hangers from the recessed wells in the ends andsides of the containers, and are joined one to the other, as thecontainers are placed into position. Connections between the containervents and the outside gas system are'made, and the sawdust or otherinsulation is blown into the open areas surrounding the mass ofcontainers. The gas escaping from the outside gas system will graduallyseep through the insulation to fill all available openings, giving adrying and refrigerating effect.

The unloading operations begin with the removal of the blown insulation,by means of the reversed blower device. The outside gas system and themetal covers are removed as the con tainers are unloaded.

All refrigerator containers, whether carload-lot orless-than-carload-lot shipment are immediately placed in the cold'roomat the receiving terminal upon arrival and the container is checked fortemperature and forcondition of the lading,

The automatic operations of the refrigerator container en route iscontrolled by the transfer of heat to the prime refrigerant and thedevelopment and intermittent release of the evolved gas of sublimationto the secondary refrigerating chambers by action of the pressurecontrol valve.

There are but two sources of heat in the interior of the refrigeratorcontainer, that which results from the oxidation of the products of thelading chamber, and that which enters the walls of the container byconduction or radiation. The heat of oxidation may be ignored, for theamount of heat so generated in a sealed container at freezing, zero orsub-zero temperature is negligible.

toLthe upper area :oflthecontainer. to .be :brought into contact.convectively; with .theconductorplate upon': which rests-- the: solid:carbon dioxide,- and will thus betransferred to therefrigerant.

A'ny heatenteringithe interioroflthe container, through the walls, willlikewise rise-by convecltive currents. to be transferred. toxtheprime'refrigerant by. contact with theconductorv plate; Allaheat sotransferred to the; prime :refrigerant will cause the sublimation ofgas; to' be.-- forced underi'th'e pressure oftheaccumulatedgas into thegas system? and the secondary refrigerating chambers;

' The. gradient step-down'principle is best described iandexplainediby'reference toFigures 14, 15' and 16,.wherein the. path: ofheat entering through the walls ofi refrigerator. containers and thetransfer of. said heat tosthecontainer refrigerant; or refrigerants,is'diagrammatically illustrated for" first, an: ordinary; refrigeratorcontainer (Figure 14) secondly; aztheoreticalrefrigerator'container(Figure 15) and thirdly, .a refrigerator: container: embodying:thegradient stepdown principle." (Figure 16)..

In Figure. l lgtheouter casing I01, the-insulation It I, the'inner'shell122; theirefrigerant chamber H1, and: a fragmentary view of. anzordinaryrefrigerator container XI are illustrated; Heat entering throughthewalls :of: thecontainer is indicated by H; H I-I jand' H? and theascending sequence indicates the direction: of flow.

From this illustration": it will.- be' observed that allv heatwhichsuccessfully*enters1the: interior of the container, by passingthrouglithewalls of the container, is ultimately brought into contactwith the refrigerant chamber; in this: case there being only onerefrigerant chamber; and; is transferred byc'o'nduction .toftherefrigerantzcausinga refrigerant consumption in? direct proportion. tothe amount" of .heat absorbed;

In' Figure 15,. then outer'c'asing 20],. the outer insulation. layer.2.32,. a: theoretical placement. of a-partfofthe refrigerantzllAb'etween-divisions of the insulation; the? inner insulation layer 23l, the inner shell 22!; the." refrigerant chamber: 2 H and a.fragmentary view" of a; theoretical.. refrigerator container. Y. are:illustrated. Heat entering through the walls of the container isindicatedxby H I, I-I ',.H ;,H ,.and El -and the? ascending sequenceindicates the direction: of" flow.

If'it were practical'to construct arefrigerator containerasidescribedzin this drawing; a part of the refrigerant would beinterposedzbetweenidivisi'ons ofv the insulatiorr in: such. a. manner asto intercept heatlentering thecontaincr before such heat reached theinterior of the container. Heat brought intocontactwiththe-refrigerating chamber .2 IslA, containingthatpart of therefrigerant interposed in the walls of the container, would,

cause-a consumption of the refrigerant inchamber 211A, and would-not.inducea transfer ofheat to=the refrigerant in chamber. 2 H, thusconserving for a longer period. oftime. that. refrigerant in chamber2-H. However, no practical gain. results from this arrangement as anactual. consumption of refrigerant occurs, partial consumption occurringin chamber- ZHA rather-than in chamber 2 t.

IniFigure. 16', component: parts of a refrigerator container embodyingthe "gradient step-down principle ofthis invention. are. illustrated. Inthe construction of this container} the outer shell I the outerinsulation.- layer 3'3, the second secondary refrigerating chamber(ductchamber) 3.9,. and its heat transfer wall 34A, the centerinsulation; layer 32,, the first secondaryrefrigerating chamber.(grooved: chamber) 35-. and. its heat transfer. wall. 34, therinner.insulationlayer 31, the inner. shell .22, theprimerefrigerant. chamber Hl andlthe. fragmentary view of therefrigerator container C are arrangedasthe component parts and apparatus of saidirefrigerator container areplaced in actual. construction. Heat entering through=the wallsofthecontainer is indicated by H, H H H H4, 11 H and H and the ascendingsequence indicatesv the directionof. the flow= Fromthe.previousdescriptiomof the construction .and operation ofthislrefrigerator container, it will be recognizedthattherprimerefrigerant (Dry Ice) is placed in the prime refrigerantchamber [Land thatthe evolved gas of sublimation accumulates in the.gas-tight chamber until the desired'pressure hasbeenbuilt up against thepressure control valve. l8 in the gas system, whereuponit is released tobeforced into the first secondary refrigerating chamber 35; which inturnforces the old,.higher-temperature gas in chamber tiinto the secondsecondary refrigerating chamber 39, the old, higher-temperature gasofthat chamber being forced from the gas system through the vent in theouter casing to the outsidegas system, or to the atmosphere. Since thesecondary refrigerating chambers are isolated againstheat transfer fromone to the other, and from all other sections of the gas system, by heatbreaker connectionsmade of poor heat-conducting material, thisrefrigerator container has three refrigerating chambers, the twosecondary refrigerating chambers so disposed astointercept heat from thesides before it reaches the interior of thecontainenand theprime-refrigerant chamber which absorbs heat reaching the interior ofthe container with the: resulting sublimation of further gasfor the.replacement of old gas which has been warmed somewhat in the secondarychambers.

Although the temperature of. the prime refrigerant, and the gasinthevarious steps of the gas system, will vary somewhat,,let us assume,for purposes. of illustration andexplanation, certain reasonabletemperatures throughout the gas system. The temperature of the primerefrigerant may be assumed. to be minus 110 F., that of the newlySublimated gas under pressure control in the prime refrigerant chamberas minus F. tominus60 F.,,that of the firstsecondary refrigcratingchamber as minus 60 F., to minus 10 F., that of the second secondaryrefrigerating. chamher as. minus. 10 F. to plus 30 F. and that of thegas being vented to the outside gas system, or to the atmosphere, asapproximately plus 30 F.

Itwill be obvious to those skilled in the art that atransfer of alargepercentage of the heat entering the Walls of the container has been madeto the cold gas of the second secondary refrigerating chamber, raisingthe. temperature of the gas of .this. chamber from minus 10 F. to plus30 F.,

after which it is vented from the container. Likewise, a large amountof, the heat which was not intercepted by the second secondaryrefrigerating chamber, throughthe medium. of .the conductor mountingplate, has. been transferred to the cold gas. of the first secondaryrefrigerating chamber, raising. the. temperature of the gas of thischamber from minus 60 F. to minus 10 F., after which the gas isforcedinto the. second. secondary refrigerating chamber- That heatwhich. did. enter the. interior of the refrigerator container, and wasbrought into conrefrigerator container.

asoassu tact with the prime refrigerant chamber for transfer to theprime refrigerant has consumed an amount of prime refrigerant in directproportion to the amount of heat transferred, and further heat enteringthe prime refrigerant chamber or chambers has raised the temperature ofthe newly Sublimated gas from minus 85 F. to minus 60 F.

If we assume all conditions of operation of the three containersdescribed in Figures 14, 15 and 16 to be the same, except that of thedifference in construction and the placement of the refrigerant, asillustrated in the three drawings, and we further assume the use of thesame weight and volume of solid carbon dioxide as a refri erant, thecombined volumes of refrigerant in chambers 2IIA and 2 of the containerillustrated in Figure 15, would be consumed in approximately the sameperiod of time as that in the container illustrated in Figure 14, whilemaintaining relatively the same temperature in the lading compartment.However, since a very large percentage of the heat entering therefrigerator container illustrated in Figure 16 is transferred to theevolved gas in the secondary refrigerating chambers, only that heatreaching the interior of the container will induce heat transfer to theprime refrigerant. Therefore, the same quantity of prime refrigerant inthis container will maintain the desired temperature in the ladingcompartment for a much longer period of time.

It will be noted in Figure 14 that the gradient I A which induces thetransfer of heat to the refrigerant is the temperature differentialbetween the surface of the outer casing and that of the interior of therefrigerator container. I In Figure 15', the gradient of thistheoretical container has been divided into two steps, step I B which isthe temperature differential between the outer casing the gradient stepIA induces the transfer of heat to the refrigerant in chamber 2i I.

In Figure 16, which is an embodiment of the refrigerator container ofthis invention and therefore an illustration of the gradient stepdownprinciple, three gradient steps are established. The'first of these,step IC is the temperature differential between the surfaces of theouter casing and the second secondary refrigerating chamber, the second,step IB, is the temperature differential between the surfaces of thesecond secondary refrigerating chamber and that of the first secondaryrefrigerating chamber, and the third, step IA, is the temperaturedifferential between the surface of the first secondary refrigcratingchamber and that of the interior of the Only the innermost gradientstep, IA, induces the transfer of heat to the prime refrigerant, andsince this is only one -:part of the total gradient of the refrigeraton,

Whi1e I .have described my invention in some detail, and with specificreference to one embodiment thereof, it will beapparent, especially tothose skilled in theart, that various modifica- -,tions may be made inthe form of the container and in the apparatus for; applyingtheprinciples spaces between said walls and between said walls '14 ofthe invention, and that certain features may be used to advantage,without a corresponding use of the other features, all without departing'from the spirit of my invention. I therefore desire, by the followingclaims, to include within the scope of my invention, all such similarrefrigerator containers, refrigerator cars, trucks, and otherrefrigerating devices, for this and all other end-use purposes, wherebysubstantially the results of my invention are obtainable bysubstantially the same means.

Iclaim:

1. In a, refrigerator container for frozen foods or the like thatrequire freezing, zero or sub- .zero temperatures, an inner shelldefining a lading compartment, an outer shell surrounding said innershell in spaced relation thereto, a plurality of intermediate walls madefrom metal of high heat conductivity and disposed between said shells inspaced relation to said shells and to each other, insulating materialdisposed in the spaces between said walls and between said walls andsaid shells, means defining at least two secondary refrigerant passagesdisposed respectively along and in heat transfer relation with respectto different ones of said intermediate walls, means disposed within saidlading chamber and adjacent the top thereof to define a primaryrefrigerant chamber adapted to contain solid carbon dioxide, arefrigerant discharge passage from said primary chamber including aconstant pressure control valve, means of low heat conducting materialconnecting said refrigerant discharge passage with one end of one ofsaid secondary refrigerant passages and connecting the other end of saidone passage to one end of the other secondary passage to transmitgaseous refrigerant successively through said secondary passages, andmeans affording a vent extending through said outer shell from the otherend of said other secondary passage.

2. In a refrigerator container for frozen foods or the like that requirefreezing, zero or sub-zero temperatures, an inner shell defining alading compartment, an outer shell surrounding said inner shell inspaced relation thereto, a plurality of intermediate walls made frommetal of high heat conductivity and disposed between said shells inspaced relation to said shells and to each other, insulating materialdisposed in the and said shells, means defining at least two secondaryrefrigerant passages disposed respectively along and in heat transferrelation with respect to different ones of said intermediate walls,means disposed within said lading chamber and adjacent the top thereofto define a primary refrigerant chamber adapted to contain solid carbondioxide and having a refrigerant discharge passage, means of low heatconducting material connecting said refrigerant discharge passage withone end of one of said secondary refrigerant passages and connecting theother end of said one passage to one end of the other secondary passageto transmit gaseous refrigerant successively through said secondarypassages, and means affording a vent extending through said outer shellfrom the other end of said other secondary passage. i

3. In a refrigeratoncontainer for frozen foods or the like that requirefreezing, zero or sub-zero temperatures, an inner shell defining alading compartment an outer shell surrounding said inner shell in spacednon-heat-transmitting relation thereto, a plurality of intermediatewalls 'rma de from metal I of high heat conductivity and dlsposecl=betweensaid shells: in spaced relationto said shells andto eachother,heatbreaker means supporting said intermediate walls, insulatingmaterial disposed in the spaces between said walls and between saidwalls and saidshells, means defining; secondary refrigerant passagesdisposed respectively along'andin heat transfer relationwithrespectetodifferent ones of said intermediate walls; means disposedwithin said lading chamber and adjacent: thetop thereof to define aprimary refrigerant chamber adapted to-contain solid carbondioxide-and'having a refrigera-nt discharge passage,- means of low heatconducting material connecting said: refrigerant, discharge passage withsaidsecondary refrigerant passages inseries and terminatingin a ventextending through said outershell.

4; In a refrigerator containerforfrozen foods or the like that requirefreezing,- zero or sub-zero temperatures, an inner shell defining alading compartment, an outer shell surrounding said inner-shell inspaced'relation thereto, means recessed into outer shell and afiording avent, a

pluralit of intermediate walls madefrom metal of" high heatconductivityand disposed between said shells in spaced relation to saidshells and toeach other, insulating material disposed in the spaces between saidwallsand said shells, means defining secondary refrigerantpassagesdisposed respectively along: and in heat transfer relation with respecttodifferent; ones of said intermediate walls, means disposed within saidlading chamber andBadjacent the top thereof'to define a primaryrefrigerant chamber: adapted to contain solidcarbon dioxide andthaving arefrigerant discharge passage means of low heat conducting materialconnectingsaid refrigerant discharge passage with said secondaryrefrigerant passages in series and terminating: at said vent.

5. In a refrigerator container. for frozen foods or the like thatrequire-freezing, zero orv sub-zero temperatures, an inner shelldefining a lading compartment, an outer shell surrounding said innershell in spaced relation thereto, means dislated by heat breakersections and disposed in heat transfer relation with said layers of heatconducting material in succession.

6. In a refrigerator container forfrozen foods or-the like that requirefreezing, zero or sub-zero temperatures, an inner shell defining alading compartment, an outer shell surrounding said inner shell inspaced non-heat-transmitting relation thereto, a ventin said outershell, a plurality of intermediate walls made from metal ofhigh heatconductivity and disposed between said shells in spaced relation to saidshells and to each other, heat-breaker means supporting saidintermediate walls, insulating material disposed in the spaces betweensaid walls and between said walls and said shells, means definingsecondary refrigerant passages disposed repectively along and in heattransfer relation with respect to different ones of said intermediatewalls, means disposed within said lading chamber and adjacent the topthereof todefine a primary refrigerant chamberadapted tocontainsolidcarbon dioxide and having a refrigerant discharge passage, and meansconnecting saidirefrigerant' discharge .passagewith saidsecondaryrefr-igerant passages in series and terminatingin said-ventandarranged to cause downward flow and then upward flow of refrigerantgases inthe successive secondary refrigerant passages.

7. In a' refrigerator container-for frozen foods or the like thatrequirefreezing, zero or. sub-zero temperatures, aninner, shell defininga lading compartment, an outer shell: surrounding said inner shell inspaced relation thereto, a. vent formed in said outer shell, a.pairofintermediate walls made from metal of highiheat conductivity anddisposed between saidshells in spaced relation to said shells and toeach other, insulating material disposed inthe spaces be.- tween saidwalls and between saidwallsand said shells, means defining two secondaryrefrigerant passages disposed respectivel alongand in heat transferrelation with respect to different ones of said intermediatewalls,means. disposed within said lading chamber and adjacent'thetop there.-of to define a primary refrigerant chamber adapted to containsolidcarbon dioxide, a refrigerant discharge passage from. said primarychamber, means of low-heat conducting material forming a connectionbetween said: refrigerant chamber and the upper end of the inner one ofsaid secondary refrigerant passages andconnecting the lower end of saidinner passage to the lower end of the outer secondary passage totransmit gaseous refrigerant successively through said secondarypassages, and means connecting theupper endof-the outer secondarypassageto said vent.

8. In a refrigerator container for frozen foods or the like that requirefreezing, zero or sub-zero temperatures, an inner shell defining alading compartment, an outer shell surrounding said inner shell inspaced-relationthereto, means disposed within said lading chamber andadjacent the top thereof to define a primary refrigerant chamber adaptedto contain solid carbondioxide, and having a refrigerant discharge.passage, means in said walls between said shells comprising alternatelayers of insulating and. of heat conductive material, means afiordingacontinuationof said discharge passage extended through saidouter shelland having sections isolated by heat breaker sections and disposed inheat transfer relation with said layers of heat conducting material insuccession, andnor-mally closed openings at opposite ends of saidinsulation layers through which dryingair may be passed to removecondensed moisture from said. insulation layers.

9. The method of loading foods and the like for transportation infrozenor sub-zero condition which consists in loading the food: or the likeinto a plurality of containers each containing a supply of solid carbondioxide adapted upon sublimation to escapefrom vents provided on theindividual containers, placing such containers in side by side relationin a freight car and in spaced relation to the walls of the freight car,supporting a perforated distributing pipe about the perimeter of thegroup of containers, and connecting the vents of said containers to'suchdistributing pipe to thereby distribute the sublimated carbon dioxidegas about the space between said containers-andthe walls-of the car.

10. The method of loading foods and the like fortransportation in frozenorsub-zero condition which consists in loading the food or the like intoa plurality of containers each containing a supply of solid carbondioxide adapted upon sublimation to escape from vents provided on theindividual containers, placing such containers in side by side relationin a freight car and in spaced relation to the walls of the freight car,supporting a perforated distributing pipe about the perimeter of thegroup of containers, connecting the vents of said containers to suchdistributing pipe to thereby distribute the sublimated carbon dioxidegas about the space between said containers and the walls of the car,and blowing insulation material into the space between said containersand the walls of said car.

11. The method of loading foods and the like for transportation infrozen or sub-zero condition which consists in loading the food or thelike into a plurality of containers each containing a supply of solidcarbon dioxide adapted upon REFERENCES CITED The following referencesare of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,864,259 Small June 21, 19321,870,685 Lockwood Aug. 9, 1932 1,895,971 Carpenter Jan. 31, 1933 VoltzJan. 2, 1934

